This invention relates to a packer system employed, for example, downhole in an oil or gas well.
Packers are expandable sealing devices, conventionally employed to seal off areas of a bore. A packer is usually cylindrical and is arranged to have, in its unexpanded state, a smaller diameter than the inner diameter of the bore of the tubing into which it is to be fitted. When a packer is passed downhole and reaches a desired location, it is made to expand by means of liquid or gas (otherwise known as expansion fluid), thereby providing a close seal against the bore. A packer system conventionally comprises a plurality of expandable packers and means for delivering expansion fluid to each of the packers. This expansion fluid delivery means usually takes the form of a plurality of pipelines known as fluid feed lines, one for each packer.
Packers are generally installed in a well in a sequence. The packers for lower regions of the well are installed first, and the rest are installed in turn, working upwards through the well.
A region of each packer is set aside to accommodate cables and tubing for the provision of downhole services to devices below the packer.
A problem which may be encountered with conventional packer systems is that, owing to the sequence of installation, packers at the top of the well are taken up with accommodating fluid feed lines for the packers below, thereby taking up space which could otherwise be used to provide downhole services.
The invention provides a packer system comprising a plurality of expandable packers and fluid delivery means arranged to supply fluid to the packers, to expand them in use, wherein the fluid delivery means includes a common pipeline for the packers.
The provision of a common pipeline, or fluid feed line, reduces the number of fluid feed lines passing through the upper packers. Therefore, more downhole services can be accommodated, if required.
Advantageously, each packer has a check valve arranged to open when the pressure of fluid in the common pipeline reaches a predetermined value. This enables the packers to be expanded in a controlled manner.
Preferably, the predetermined value at which each valve opens is different for each of the packers. This allows the packers to be expanded in sequence, which sequence can be determined by an operator of the system.
The packer system can also include devices arranged to prevent the packers from contracting after they have been expanded. These devices may be ratchet mechanisms or non-return valves, or a combination of both.
The common pipeline may be arranged to supply fluid to a downhole device actuator, after expansion of the packers. The actuator may have a valve arranged to open when the fluid in the pipeline reaches a predetermined value, which value is preferably greater than the working pressure of the actuator.
The invention further provides a method of installing a packer system, which system includes a plurality of expandable packers in predetermined locations, comprising supplying fluid to the packers, to expand them, via a common pipeline.